Carbon nanotubes in space elevators: Nicolas Pugno showed that the strenght of macroscale CNs is reduced to a theoretical limit of 30 gigapascal, with a needed strenght of 62 GPa for some desings… Whats the state of the art in tensile strenght of macro-scale CNs? Any other thoughts related to materials for space elevators?
I just read an article raising a point which is so obvious in retrospect that I’m shaking my head that it never occurred to me.
Boron Nitride nanotubes have a very similar strength to carbon nanotubes, but much much stronger interlayer coupling. They are a much better candidate for this task.
I’m not really up to speed on that, being more on the electronics end. Still, I’ve maintained interest.
Personally, every year or so I check in with the NASA contest to see how they’re doing.
Last I heard, pure carbon nanotube yarn was a little stronger by weight than copper wire. Adding a little binder helps a lot.
Pugno’s assumption of 100 nm long tubes is very odd—you can grow much longer tubes, even in fair quantity. Greater length helps a lot. The main mechanism of weakness is slippage, and having longer tubes provides more grip between neighboring tubes.
This is more in the realm of a nitpick, though. If I were to ballpark how much of a tensile strength discount we’d have to swallow on the way up from nanoscale, I would have guessed about 50%, which is not far off from his meticulously calculated 70%.
I’d love for space elevators to work; it’s not looking promising. Not on Earth, at least. Mars provides an easier problem: lower mass and a reducing atmosphere ease the requirements on the cable. My main hope is, if we use a different design like a mobile rotating skyhook instead of a straight-up elevator, we could greatly reduce the required length, and also to some extent the strength. That compromise may be achievable.
Carbon nanotubes in space elevators: Nicolas Pugno showed that the strenght of macroscale CNs is reduced to a theoretical limit of 30 gigapascal, with a needed strenght of 62 GPa for some desings… Whats the state of the art in tensile strenght of macro-scale CNs? Any other thoughts related to materials for space elevators?
I just read an article raising a point which is so obvious in retrospect that I’m shaking my head that it never occurred to me.
Boron Nitride nanotubes have a very similar strength to carbon nanotubes, but much much stronger interlayer coupling. They are a much better candidate for this task.
I’m not really up to speed on that, being more on the electronics end. Still, I’ve maintained interest. Personally, every year or so I check in with the NASA contest to see how they’re doing.
http://www.nasa.gov/offices/oct/early_stage_innovation/centennial_challenges/tether/index.html
Last I heard, pure carbon nanotube yarn was a little stronger by weight than copper wire. Adding a little binder helps a lot.
Pugno’s assumption of 100 nm long tubes is very odd—you can grow much longer tubes, even in fair quantity. Greater length helps a lot. The main mechanism of weakness is slippage, and having longer tubes provides more grip between neighboring tubes.
This is more in the realm of a nitpick, though. If I were to ballpark how much of a tensile strength discount we’d have to swallow on the way up from nanoscale, I would have guessed about 50%, which is not far off from his meticulously calculated 70%.
I’d love for space elevators to work; it’s not looking promising. Not on Earth, at least. Mars provides an easier problem: lower mass and a reducing atmosphere ease the requirements on the cable. My main hope is, if we use a different design like a mobile rotating skyhook instead of a straight-up elevator, we could greatly reduce the required length, and also to some extent the strength. That compromise may be achievable.